DC SPECIAL SERIES is another series that went through some wild changes in its last few issues. From 1977-1979 being a sporadic giant-size special of pretty nice new and reprint material (the highlight for me being a complete reprint of the Wein/Wrightson SWAMP THING series, the first two issues with new wraparound Wrightson covers, and the BATMAN SPECIAL with work by Nasser, Rogers and Golden).

Then with 18 and 19, went to a digest-size format.
Then back to a comic in 20-22.
Then back to a digest in 23-24, then a tabloid 11 X 14" size like LIMITED COLLECTORS' EDITION for issues 25 and 26, and a Marvel/DC crossover (SUPERMAN VS. HULK) for the last issue!

If you don't know the title to search under, that last issue is really hard to find.